A conventional tank-type vacuum circuit breaker has a structure shown in FIG. 5. In a pressure tank 1 that is electrically grounded and filled with an insulating gas, a vacuum interrupter 7 is electrically insulated from the wall surface of the pressure tank 1 and supported horizontally. A moving electrode 10 of the vacuum interrupter 7 is connected to an insulating rod 12 that electrically insulates the electrode 10 from an actuation mechanism 11 of the breaker, then passes through a flange 4 that closes an opening 3 of the pressure tank 1 through a flexible bellows 13 that enables an opening and closing actuation of the breaker from the outside of the pressure tank 1 by the actuation mechanism 11 with the pressure tank 1 kept airtight, and then is coupled to the actuation mechanism 11.
On the other hand, at one end of the pressure tank 1 to which a stationary electrode 9 of the vacuum interrupter 7 faces, another opening 32 for working is provided to allow the vacuum interrupter 7 to be inserted into or taken out from the pressure tank 1 in replacing the vacuum interrupter 7. The components from the working opening 32 to the actuation mechanism 11 are directly aligned in the horizontal direction. Note that the working opening 32 is normally sealed with a lid plate 33.
Furthermore, one pair of openings 17a and 17b facing upward are provided in the pressure tank 1. The vacuum interrupter 7 is electrically connected to bushing terminals 22a and 22b through: terminals 14a and 14b; compartment spacers 18a and 18b passing through the openings 17a and 17b while keeping electrical insulation from the pressure tank 1 and keeping the pressure tank 1 airtight; and conductors 21a and 21b passing through current transformers 23a and 23b and bushings 20a and 20b. 
Another tank-type vacuum circuit breaker has an airtight compartment collectively including those components from the vacuum interrupter to the bushing terminals without the compartment spacers (for example, see PTL 2).